A video signal is generated representative of a background scene, such as a weather map, which provides an outline of all the detail in the map. This outline detail is made visible to a foreground subject by projecting it onto a white screen behind the subject in a selected color such as green. The projector is selectively inhibited so as to prevent the background detail from projecting onto the foreground subject. The white screen and the green detail lines are removed and replaced by the background scene by an image compositing process. Prompts are visible to the foreground subject, but not visible to a home viewing audience.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A method for projecting and then removing visible prompts comprising the steps of: a) computing reference RGB color ratios of a white screen, b) generating a binary matte signal from said color ratios that identifies areas of said white screen unobstructed by a subject as those pixels in a current image whose color ratios match reference color ratios, and all remaining pixels identify a subject area, c) generating a detail signal of a background scene by differentiating its red, green and blue components, d) inhibiting said detail signal in said subject area, e) projecting said inhibited detail signal onto said white screen, f) removing from a camera signal said projected inhibited detail signal by reducing the level of the color of each pixel of said detail signal to a level that results in the pixel's color ratios equaling those of the white screen, g) generating a linear matte signal by calculating the percent contribution of the background to the image in a current frame, h) removing the contribution of the background scene from a current image frame, by subtracting the product of the linear matte signal and a selected clear frame signal, to create a processed foreground image for use as input to a compositing system.
2. The method of claim 1 in which said color ratios, when using a green colored detail image, are r/b, g/r, and g/b, where r, b and g represent respectively, red, blue and green signal components of a current image frame.
3. The method of claim 1 in which said detail signal is generated by selecting the larger of the separate r g b detail signals if one of said detail signals is greater than 0.5, or the sum of r g b detail signals if none are greater than 0.5, as the detail signal selected for projection.
4. The method of claim 1 in which said detail signal is assigned one of the colors green, blue or red.
5. The method of claim 1 in which said projector is an electronic projector.
6. The method of claim 1 in which said projected inhibited detail signal is assigned a green color and is removed by assigning each pixel in the white screen area, unobscured by elements of the foreground subject, a signal level of g where g r(G/R), where r represents a red signal component of a current image frame, R represents a red signal component of a white screen image frame and G represents a green signal component of said white screen image frame.
7. The method of claim 1 in which said linear matte signal is the percent contribution of the background scene to each pixel in the image frame, and is computed for the transition area by the equation C (y x)/(z x) where x is the rgb levels of a pixel on the edge of the opaque subject; where y is the rgb levels of a given pixel in the subject to background transition area; and z is the rgb signal levels of pixels on the white background.
8. The method of claim 1 in which said selected clear frame is one of two clear frames where the first of said two frames is an image of the white screen background with foreground subject removed prior to the storage of the clear white screen frame, and the second clear frame is a current image frame that includes the subject, and where said subject is removed by at least one of interpolation and extrapolation of r g b levels on the white screen adjacent to the subject, across said subject thereby removing the subject but leaving subject shadows if present.
9. The method of claim 1 in which said white screen comprises a translucent white material.
10. The method of claim 9 in which said translucent white material is illuminated from its rear to control shadow density.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
August 7, 2002
September 9, 2003
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